Piston cooling nozzles (PCNs) are known. In general, PCNs deliver oil to the pistons of an internal combustion engine to transfer heat away from the pistons. During operation, some of the heat resulting from fuel combustion is absorbed by the pistons, causing an undesirable temperature rise. Without adequate heat transfer away from the pistons, the carbon deposits may be increased on the pistons. One way to reduce this excess heat is through use of PCNs.
A PCN generally has an inlet which receives relatively cool oil from the engine's oil distribution system and an outlet which directs the cooled oil toward the piston associated with the PCN. The cool oil contacts surfaces of the piston to transfer heat away from the piston.
Delivery of the cooled oil to the desired locations on the piston is a performance specification taken into consideration during the design of the PCN. Not only is it desirable to deliver the oil to the surfaces of the piston yielding efficient heat transfer, it is more fundamentally desirable to avoid contact between the PCN and the piston or other moving parts. In certain engine designs, it has been observed that the connecting rod coupled to the piston contacts the tube portion (further described below) of the PCN during engine operation. Of course, repeated contact during the cyclical operation of the connecting rod leads to wear of the tube portion. This wear may manifest itself as a thin wall in a section of the tube portion (i.e., a flat spot on the outer diameter of the tube portion), or even a hole through the tube portion side wall, seriously impairing the PCN's ability to deliver oil to the piston as desired. In fact, the wear may ultimately lead to bending or breaking of the PCN, which may result in catastrophic engine failure.
As the discussion above indicates, precise mounting of the PCN is desirable to permit proper operation and avoid interference with the moving components of the engine. To date, PCN orientation is determined by either a machined locating feature on the engine block or a special interface formed on the block during casting. While machined locating features may permit very precise mounting of the PCNs, the design of some engine blocks makes machining a locating feature difficult to accomplish or otherwise undesirable. On the other hand, since a casting process is not as accurate as a machining process, the orientation of the PCN based on a cast feature of the block can vary somewhat relative to its preferred position due to surface inconsistencies and the relatively loose tolerances of the cast block.
One approach to improving the mounting accuracy of PNCs on cast engine blocks is described in U.S. Pat. No. 7,240,643, which is assigned to the present applicant. The approach described in the '643 patent includes brazing a metal tab or bracket to the tube portion of the PCN which functions as a spacer that is indexed off of the bottom end of the corresponding cylinder liner. While this approach is desirable for a variety of reasons set forth in the patent, an alternative PCN configuration may be better suited for certain engine designs.